Control of alternating-current motors.



No. 841,257. PATENTED JAN. l5, 1907 M. C. A; LATOUR.

CONTROL OF ALTBRNATING CURRENT MOTORS.

APPLICATION FILED NOV.9, 1905.

wmis Nmfm: i Marius, C. .Lva our, M M-f HMM f fami.-

imirnn srrirns PATENT cerros.

MARlUS C. A. LATOUR, OF PARiS, FRANCE, ASSIGNCR lC GENERAL ELEC- TRCCOMPANY, A CCRPCRATICN OF NEW YORK.

CONTF'ZQL F ALTERNATBNG-CURHENT MOTQRS.

Speeicaton of Letters Patent.

Patented Jan. 1 5, 1907.

Application filed November 9,1905. Serial No. 286,509.

To (if/ZZ 111710110 t 712er/ Ifo/merit:

Be it known thal l, lviAniUs C. A. LATOUR, a citizen of France, residingat Paris, France, have invented certain new and useful lmprovements inControl ol: Alternating-Current Motors, oiE which the following is aspeciiication.

My invention n lates to the control of alternating-current motors oi thetyp-c known xo as compensated series motors; and its object is toprovide a n/ovel arrangement for4 motors of abled to chronism. Thecompensated series which term is understood in the art a. series motorhaving a winding on the field structure arranged and connected toproduce a magnetomotivc force, neutralizing the armature,self-induction, and reaction, operates very poorly above synchronism .asregards sparking.

My invention consists in motor-armature in a closed circuit with a 2 5source of voltage of proper phase for producing a current ior producinga. commutating field. The commutating iield thus produced improves thecommutation of the motor, so

as to render it possible to run the motor at 3o speeds greatly abovesynchronism.

More specifically stated, in order to obtain the proper phase oilI thecurrent in the local circuit employ a source of voltage having onecomponent dependent in phase on the 3 5 impressed voltage and the otherdependent in phase on the motor-currents. By properly adjusting themagnitude el these'two components a voltage of the proper phase andamount in the closed circuit may beobtained.

In order to avoid the necessity of employirngT auxiliary apparatus, suchas a series transformer, to obtain the component voltage in the localcircuit dependent in phase on the motor-currents, my invention furtherconsists in forming the local circuit by establishing a connection fromthe armature-terminal, not already connected to the motor-field througha source of voltage to a point on the field-Winding. By thus including aportion of the field-Winding in the local circuit the component voltagedependent in phase on the motor-current is obtained, the effect beingLhis type whereby they are enoperate sparklessly above synmotor, by

reference to the armature, F the field,

connecting the electrically the same as though a series transformer wereemployed ior this purpose.

My invention will best be understood by accompanying drawings, inWhich-- Figure 1 shows diagrammatically a compensated series motor, thisbeing the type of motor to which my invention relates. Fig. 2 is adiagram showing the circuit connections for operation in accordance withmy invention, and Fig. 3 shows a modified arrangement of circuitconnections.

ln the drawings, A represents the motorand C the compensating winding.The armature is provided with the usual commutator B and brushes l) t.All three windings are connected in 7o series in the usual manner. Thefield-Wind ing F produces a held at right angles to that produced by thearinature-currents, and the compensating winding C produces a field inline with the armature reaction, so as to 7 5 neutralize the armaturereaction and selinduction in the manner well understood in the art.

In Fig. 2, 'll represents a. trai'isiormer or other suitable source olalternating current. c represents a connection established between anintermediate peint on the secondary of transformer l and an intermediatepoint of the vfield-vvinding l?. By means of this connection a localcircuit is formed, including the armature ol the motor, a portion of thesecondary of transformer T, and a portion of the Held-winding l-`. l nother words, the arf mature A is included in a closed circuit with asource ol voltage of which one coniponent` viz., that produced by thesecondary of transformer rl"is in phase with the voltage iinpressed onthe motor, while the otlicrcompenente-viz., the voltage across theportion ol the held-winding lP included in the closed cir- 9 5 cuit---isdependent in phase upon the current in the motor. Vlhis latter componentlags substantiallyninety degrees behind the inotor-current, since thisvoltage is produced. bv and is consceuentlyv ninety degrees behind theflux interlinked with the 'held-winding F, and this flux is in phasewith the motor-current. Il' these two components are selected withproper relative magnitnde-that is` if the proper proportion of turns-ofthe, transformer T and of the field-Winding F are in- CLN IOO

'the motor.

@i senese the proper phase and amount for enabling' the motor to operatesparklessly at 'an given speed Within limits. By varying the tWocomponents of the voltage in the closed cir-v cuit the motor may beadjusted for substantially sparldess commutation .over widely-varyingspeeds above synchronisin. The phase of the voltage desired in theclosed circuit, consisting of the armature, the portion of the field,and the portion of the transformer T, will appear from the ollcWinconsiderations: In the ordinary compensate series motor the sparking isdue to the electrornotive force induced in a coil short-cin cuited by abrush by the alternating field of Thisl held is in phase with themotor-current and the electromotive force induced by this field in theshort-circuited coil laws ninety degrees behind .it-that is, the voltagethat produces the commutation troubles lags ninety degrees behind themotor-current. Consequently in order to secure perfect commutation it isnecessary to induce in the short-circuitcd coil a second electromotiveforce which must be opposite in phase to the first and which mustconsouently also be ninety degrees out of phase withl the'motor-current.Since this electro- 'motive force is to he produced dynamically by theshort-circuited coil cutting the comrnutating iield, it will be in phasewith the coninrutatin@ iield. Consequently it is dcsircd to produceacommutating field which is ninety degrees out oi phase with themotor-currents. Since the closed circuit through which the Current whichproduces the commutating iield tlm highly inductive,'this current, whichproduces the comn-u Lin(Y field, will substantially ninety ees ehind thevoltage which produces and since this current, which produces thecommutating field, must be ninety decrees behind the main motor-current,the voilage which produces it must loe in phase with, or rather inopposition to, the mein motor-current. The voltage which producesthecurrent which in turn produces the commutatingI vfield is resultantvoltage formed by three cornponents-namely, the counter electromotivei'orce of rotation ol the armalure, the eieetromotive force across theterminals of the portion of the field-wimling included in.

the local closed circuit, and the electromotive force across theterminals ol' that portion of' the secondary of transformer 'l which inluded in the closed chr-uit. Ul' these three he counter electromotivcforce of rotation d.i'el )pcd in the arma-lure is in phase with the mainmotor-field, and consequently with tage.

I the main motor-current-that is, it is of the same phase with thedesired resultant vol- This counter electromotive force, however, isfixed by the field strength of the motor and the speed of rotation, andconsequently it cannotbe adjusted as desired for varying speeds. Theother two voltagesnamely, the potential across the portion of `theheld-Winding and across the portion of the transformer, the first ofwhich is displaced ninety de rees from the main motorcurrent, as has eenheretofore explained, and the second of which is in phase with theimpressed voltage, and consequently out of phase with the mainmotorcurrent by an.

angle corresponding to the angle of lag ofthe main niotor-current-may beso prop ortioned that these two components will give a resultant inphase with, or rather in o position to, the main1notor-currentonsequently the resultant of the three voltages is inopposition to the main motor-current, which is the phase relationdesired, and since two of the components are adjustable the resultantvoltage may be adjusted for the desired value and still maintained atthe proper' phase. it will be seen 'that since this current whichproduces the commutating iield flows through a portion of' theheld-winding F, and is substantially ninety degrees out of phase withthe main 1notor-current, it will produce a certain shifting of the phaseof the field' produced by the Winding F, and this shifting'somewhatmodiiies the phase relations as stated above. This variation,hoW- over, may easily be taken account of in adjusting' the relativeproportions of the voltages taken from the held-winding F and thetransforrmr 'l in the local circuit.

lVhile the connections which 'l have described above for obtaining a comonent voltage if the closed circuit depen( ent in phase on themotor-circuit obviate the necessity of 'usingany additional apparatus,nevertheless it is obvious that such a coinponent voltage may beobtained in other ways if desired. rl`hu's in Fig. 3 a seriestransformer S is employed i or this purpose,

and it will be seen that this arrangement isries motor l'oralternufinf;` currents, a local ein lit comprising the motor-arnratureand a senese oli voitege inning componentde- "indent in phese on theimpressed Voltage nel L second component dependent in phase on 'then'iotoneurrent,

3. in combination with e compensated series nio'lor having onearmature-terminal oonneeied directly to one eld-tenninel, e oonneeifionfrom the other armature-terminal lnougli e sour-ee of voltage to pointon the eld-vwinding.

il. In combination With a. compensated se- ;i motor for elternetingcurrents, e local eii'enit comprising the motor-armature and a souee el"Voltage having one component in phase with the impressed voltage and aseeond component dependent in phase on the motor-current.

5. in combination with compensated se'- nio'or for alternating ouientsIa local circuit comprising he inotor-arniatuie and e source of Voltagehaving one oon'iponent in phase with the iinpressedvolmge and a seoondcomponent dependent in phase on the inotfoiourrent, and means foradjusting the relative magnitudes of said components.

6. In combination with compensated seies motor having onearmziture-terininal connected directly to one field-terminal, econnection fr-ziin the other armature-terminal thi'ougli asouioe ol'voltage to ay point on the field-winding, and means for shifting seidpoint on the i'ield-winding.

'n witness whereof ll. lieve hereunto set my hand this 8th dey olINovember, 1905.

MARUS C. A. LATOUR.

Witnesses BENJAMIN B. HULL, MARGARET E. WOOLLEY.

